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Overview

Wallet providers need to support the dataSuffix capability to enable attribution. This involves accepting the capability and appending the suffix to the calldata before signing.
1

Support the dataSuffix Capability

Your wallet should accept a dataSuffix object in the capabilities object of wallet_sendCalls.
type DataSuffixCapability = {
  value: `0x${string}`;  // hex-encoded bytes provided by the app
  optional?: boolean;    // whether the capability is optional
}
2

Append Suffix to Calldata

When constructing the transaction or User Operation, extract the dataSuffix and append it to the calldata.
Append to tx.data.
// Minimal example for EOA
function applySuffixToEOA(tx, capabilities) {
  const suffix = capabilities.dataSuffix?.value
  if (!suffix) return tx

  return {
    ...tx,
    // Append suffix bytes (remove 0x prefix from suffix if tx.data has it)
    data: tx.data + suffix.slice(2)
  }
}
3

Add Wallet Attribution (Optional)

Wallets may also include their own attribution code (their own ERC-8021 suffix) by prepending the wallet’s suffix before the app’s.
  • No interaction required with apps: The wallet handles this independently.
  • Multi-code support: ERC-8021 natively supports multiple attribution codes.
Example:
finalSuffix = walletSuffix + appSuffix
This ensures both the app and the wallet receive onchain attribution.